This specification relates to a printed circuit board (PCB) and an integrated circuit (IC) package.
An IC chip, such as an application-specific integrated circuit (ASIC) chip, can be attached to a substrate and coupled to a PCB, using solder balls to establish electrical connections with the PCB. Circuitry on the device formed by coupling the IC chip, the substrate and the PCB together can be used to transfer data in data networks, data centers, and many other suitable applications. For high-speed applications, such as serializer/deserializer (SerDes) input/output (I/O) in networking switch ASIC chips, electrical connections with the PCB may be established using flip chip ball grid array (FCBGA), in which the chip die is flip chip bonded to one side of the substrate while solder balls are attached to the other side of the substrate in a particular arrangement, where the solder balls are periodically placed in multiple rows and columns at a certain pitch. The solder balls attached on the substrate are flipped over to be coupled with bonding pads of a PCB.
There is a continuing need to increase the ASIC SerDes I/O connections to meet increasing networking data demand and data bandwidth demand. This has led to a need to increase the number of ball grid array (BGA) solder balls in an IC package to accommodate the increased I/O demand. With the I/O bandwidth becoming higher, the corresponding core logic is increased accordingly to process the increase in data bandwidth. This leads to a larger core logic power requirement, and BGA solder balls with greater power carry capacity are required to prevent electro-migration and to lower voltage drop. However, the BGA solder ball counts are limited by the package size and BGA pitch. The package size is limited by manufacturing issues such as substrate warpage, solder ball co-planarity, and the yield of the apparatus process. Lowering the BGA pitch is one way to get more BGA solder balls in a limited size package. However, smaller BGA pitch requires smaller BGA ball size because of manufacturing and assembling process limitation. Smaller solder ball means lower current capacity. Furthermore, small pitch BGA signal escape becomes difficult inside BGA field on PCB.